Mechanical elements with negative stiffness may be used in the design of mechanical isolation systems, in which they may be combined with elements having positive stiffness to result in an assembly with low stiffness. In another application, a negative stiffness element may be employed as a resettable mechanical fuse, which, when subjected to a force exceeding a predetermined threshold, gives way, thereby preventing the force from exceeding the threshold. Such a fuse may be used to protect a sensitive mechanical system from shock forces exceeding this threshold.
Although certain designs for negative stiffness elements are known in the art, they are generally large, complex, and capable of providing relatively low values of negative stiffness. In particular, the specific negative stiffness, i.e., the maximum negative stiffness per unit volume or per unit mass, is typically low. This makes these designs inconvenient or difficult to use for providing, for example, shock protection in a small volume. Moreover, existing designs are typically complex structures several of which cannot readily be combined to form a single compound structure with a larger value of negative stiffness.
Thus, there is a need for a compact, stackable negative stiffness element providing a large negative stiffness.